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Vol. XXXVII. 



LONDON, AUGUST, 1905. 



No. 8 



Fig. 



PRACTICAL AND POPULAR ENTOMOLOGY.— No. 8. 

 A Method of Measuring Insects. 



BY J. R. DE LA TORRE BUENO, NEW YORK. 



The common callipers ordinarily sold for measuring insects have 

 always seemed to me too coarse for fine work. In the Hemiptera 

 especially, where there is an abundance of small forms, they would cer- 

 tainly be useless for the delicate measurements of antennae and limbs so 

 frequently necessary, and for the proportional dimensions called for in the 

 determination of species. While endeavouring to solve this problem, my 



set of drawing instruments came to my 

 mind, and with the bow-dividers (Fig. 12) 

 the difficulty was partially solved. I ground 

 the points flat and parallel, to knife-edges. 

 Now, by means of the screw of the dividers 

 and by the use of a magnifier, it was possible to make direct measure- 

 ments of parts of an insect, such as diameter and length of limbs and 

 antennaj, dimensions of the segments, etc. The next oroblem was an 

 accurate scale. In looking over the machine-tool catalogue of Brown & 

 Sharpe, Providence, R. I., I ran across' the cut of a little steel scale 



(Fig- 13) 5 cm. long, 

 graduated on one side 

 to centimeters, milli- 

 meters and 5ths of a 

 millimeter ; and on the 

 other to inches, halves, quarters, eighths, 64ths and looth. With these 

 two appliances I can make measurements to within one-tenth millimeter 

 or less. As to the manner of using them, whoever has the instruments 

 will at once see the way, without my entering into a prolix explanation. 

 The cost of the scale is trivial (25 cents); the dividers are more expen- 

 sive. I believe they cost something more than a dollar, 



Fif>-. 



